U.S. Pat. No. 6,418,972 (Krumm et al.) and corresponding German Patent Laying-Open Document 100 21 520 A1 disclose a direct drive for the reed of a loom of the general type mentioned above. The entire disclosure of U.S. Pat. No. 6,418,972 is incorporated herein by reference. The known direct drive arrangement comprises an integrated direct drive electric motor and does not require any intervening transmission means between the electric motor and the reed. A first embodiment of the known arrangement involves a circular coaxial drive that is arranged essentially rotationally symmetrically about the reed support shaft, which carries the reed to cause a pivoting oscillation of the reed about the axis of the reed support shaft. A second embodiment of the known arrangement involves an arcuate “linear” drive that oscillates or pivots in an angularly synchronous manner with the reed along an arc path. In this linear drive, the pivot or oscillation axis of the oscillating motion of the reed is located within the structural elements of the reed or the reed drive.
It should be noted that the prior art “linear” drive does not involve true straight line linear motor components producing a straight line linear motion, but rather refers to a motor with arcuate components that produce an arcuate pivoting motion so that the reed oscillates or pivots back and forth along an arc path. In both embodiments of the known arrangement, the reed support shaft itself can be either a stationary fixed component or a moving component, about which the reed pivots in an oscillating manner, or the reed is rigidly fixed to the reed support shaft, which forms the rotor and pivots about its own longitudinal axis.
In both embodiments of the known arrangement, either the fixed component of the motor carries permanent magnets while the movable component of the motor is energized with a driving current, or the movable component of the motor carries the permanent magnets while the fixed or stationary component of the motor is energized by a driving current. Alternatively, at least a part or portion of the motor may be both provided with permanent magnets and energized with a driving current.
In view of the relatively small available installation space for the known embodiments of the direct drive arrangement, it is difficult to develop the rather large rotational moments or torques that are required for driving a typical reed of a modern high speed loom. Thus, it has been found that both embodiments of the known direct drive arrangement are preferably to be improved in order to increase the rotational moments or torques that can be achieved. It should further be noted that attempts to increase the size of the known arrangements by allocating a larger installation space for each respective drive arrangement would undesirably increase the total space requirement or bulkiness of the drive, and would also disadvantageously increase the total mass and the associated inertial moment of the moving components of the drive arrangement itself, which in turn would directly increase the required torque for achieving the required drive power. Therefore, some other technical improvement is still desirable.